The use of a power takeoff device (herein referred to by its common abbreviation “PTO”) in association with truck or other vehicle (or stationary engine) transmissions is generally known. Generally speaking, such PTO's often include an input gear, an output gear and a mechanism for engaging the input gear with the output gear so as to rotate the output shaft of the PTO to power an auxiliary device to perform useful work when desired. The mechanism also provides a means for disengaging the input gear and the output gear.
In certain conventional designs, the input gear of the PTO is constantly engaged with the appropriate gear in the vehicle's transmission when installed on the vehicle and is, thus, continuously turning whenever that gear in the vehicle's transmission is turning. In order to provide for selective rotation of the output shaft of the PTO (associated with the output gear), a clutch mechanism is frequently provided between this input gear of the PTO and the output gear. When this output shaft is rotated, useful auxiliary work can be performed. For example, the output shaft may be connected to a hydraulic pump that may be used to operate auxiliary equipment, such as garbage compacting bodies, dump bed bodies (a/k/a, “dump trucks”), garbage trucks or trailers, winches, post hole diggers, and the like. Example PTOs are disclosed in U.S. Pat. No. 5,542,306, issued Aug. 6, 1996; U.S. Pat. No. 7,070,036, issued Jul. 4, 2006; and U.S. Pat. No. 7,159,701, issued Jan. 9, 2007.
One type of conventional PTO clutch is operated through an aligned multi-disc stack arrangement located between the shaft of the PTO and the gears of the PTO which engage with the gears of the truck's transmission. When an axial force is applied to the disc stack, the individual discs in the stack are forced together such that the interfacial friction between the discs cause the shaft to be rotationally joined to the rotating gears. Engagement and disengagement of the clutch is frequently effected by an electrically operated solenoid valve arrangement, the switch for which is frequently located (along with an appropriate warning light) in the cab of the truck.